This invention relates to a mounting system for hingedly mounting the halves of a thrust reverser cowl to an engine core, and more particularly relates to a system wherein two hinges are provided and an additional third load transfer means is provided to transfer the cowl loading to the engine mounting strut.
A typical thrust reverser structure for use with a turbofan engine consists of two semicircular duct halves, known as C-ducts, both hinged to the engine mounting strut so that the C-ducts can be pivoted to an open position spaced from the engine core for maintenance of the engine core and the thrust reverser itself. Each of the C-ducts pivots about a hinge line that is necessarily a straight line common to both the strut and the thrust reverser cowl. The cowl itself, however, is aerodynamically shaped and is narrower at the rear than at the front so that the hinge line is substantially outside the contour of the cowl at the rear portion of the thrust reverser cowling. Typically, three hinges are utilized to attach each C-duct to the engine mounting strut, with the third, or aft, hinge having to be specially arranged to operate on the hinge line outside the contour of the cowl. The cowl itself has to be modified by the addition of a fairing to cover the third hinge to reduce the aerodynamic drag of the hinge. The addition of the fairing adds significantly to the weight and peformance benefits of the aircraft. In some cases, the hinge line has been relocated downwardly to reduce the out-of-contour condition of the aft hinge. On some installations this is acceptable but adds significant weight penalties. On other installations strut construction dictates where the hinges must fall to optimize load path and the hinge line cannot be moved and, therefore, the addition of an aerodynamic fairing is unavoidable.
The most obvious solution to the problem of the third out-of-contour hinge is to simply eliminate the hinge. However, due to the enormous loads reacted into the strut from the reverser during flight conditions, it is necessary that there be at least three load transfer points to transfer the reverser load to the strut, and all reversers presently in service on commercial aircraft have at least three cowl hinges, and some more than three.
The third hinge is not needed to move the cowl into the open or maintenance position, nor is the third hinge needed to accommodate the load of the C-duct in the maintenance position when it is out of service. Therefore, in the maintenance and opening operations the third hinge could be completely eliminated. However, as discussed above, the third hinge is mandatory structurally to handle the load transfer from the thrust reverser to the engine mounting strut during operation of the aircraft.